Sperm cells are highly vulnerable to free radicals, and sperm quality and male fertility are critically affected by oxidative stress. Recently, sexual ornaments, particularly carotenoid-based colourful traits, have been proposed to depend on a male's capacity to resist oxidative stress, and thus to signal sperm quality. We conducted an experimental test of this hypothesis on great tits Parus ma...

Environmental philosophers spend considerable time drawing the divide between humans and the rest of nature. Some argue that humans and our actions are unnatural. Others allow that humans are natural, but maintain that humans are nevertheless distinct. The motivation for distinguishing humans from the rest of nature is the desire to determine what aspects of the environment should be preserved....

Abstract Generalised regression estimation allows one to make use of available auxiliary information in survey sampling. We develop three types generalised estimator when the data cannot be matched perfectly sample units, so that standard is inapplicable. The inference remains design-based. Consistency proposed estimators either given by construction or else can tested observed and links. Mean ...

We study the fundamental question of how query learn ing performs in imperfectly learnable problems where the student can only learn to approximate the teacher Considering as a prototypical sce nario a linear perceptron student learning a general nonlinear perceptron teacher we nd that queries for minimum entropy in student space i e maximum information gain lead to the same improvement in gene...